The overall objective of the proposed research program is to further examine the hypothesis that the lymphatic vascular system is an extensive system like the blood vascular system, i.e. arteries and veins, however, its function is different. To further explore this hypothesis, lymphatic endothelial cells will be isolated from bovine mesenteric lymphatic vessels to establish primary cultures. From these homogenous cell cultures of lymphatic endothelial cells stable clones will be established and their growth requirement determined. In addition, detailed cellular characteristic studies using phase contrast microscopy, ultrastructural and immunocytochemical methods will be carried out on cloned lymphatic endothelial cells. Once viable clones are established cell membrane proteins of the lymphatic endothelium will be isolated and used as immunogens for the production of monoclonal antibodies. The antibodies obtained will be used to recognize lymphatic endothelial cell surface membrane antigens, in addition such a marker would be very important for identifying lymphatic endothelial derived tumors. Now that we have been able to isolate lymphatic endothelial cells and successfully grow and maintain the lymphatic endothelium in long term culture, we can focus our skills on bringing the current methods and techniques of cell biology, biochemistry, immunology and molecular biology to bear on investigating the morphological, functional and pathophysiological activities of the lymphatic endothelium. Results from these studies will identify specific cellular, immunologic and biochemical features of the lymphatic endothelium that will provide new information to further explain the mechanisms involved in the function of the lymphatic system in health and pathological processes.